From the Archives: Circadian Rhythms

circadianrhythm

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This year’s Nobel Prize in Physiology and Medicine was awarded to three men who did basic research, discovering molecular mechanisms that control the circadian rhythm. The discoveries by Jeffrey C. Hall, Michael Rosbash and Michael W. Young “explain how plants, animals and humans adapt their biological rhythm so that it is synchronized with the Earth’s revolutions,” write the Nobel committee.

They and other researchers have continued to add details to our understanding of this critical system. In a story for Cerebrum in 2014, Paolo Sassone-Corsi described two relatively new areas of research: circadian genomics and epigenomics:

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Monitoring the Body’s Invisible Clock

Our body is regulated by an invisible clock that influences our wakefulness, sleep, thoughts, and emotions. The circadian clock is an important regulatory feature, yet neuroscientists still don’t completely understand it. Although cognitive tests can be performed, it was difficult to monitor brain cells over the course of a day until neuroscientist and Dana Alliance member Huda Akil, M.D., designed an experiment that gave a new perspective on circadian clocks.

“Maybe it’s simple-minded, but nobody had thought of it,” she said to The New York Times in a recent article. Her team examined the healthy brains of 55 donors who had died suddenly at different times of the day. As reported by the Times:

As each person died, his brain cells were in the midst of making proteins from certain genes. Because the brains had been quickly preserved, the scientists could still measure the activity of those genes at the time of death.

Most of the genes they examined didn’t show any regular pattern of activity over the course of the day. But they found that more than 1,000 genes followed a daily cycle. People who died at the same time of day were making those genes at the same levels.

The findings were so consistent that they even enabled the scientists to determine the time of death within the hour.

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A Wake-up Call on Sleep Disorders

Too many of us live by the catchphrase, “sleep when you’re dead.” When it feels like there is more to do than the day allows, we surrender our sleep hours and then make up for it by consuming an excessive amount of caffeine the next day. After a few days, we’re so exhausted that we can hardly hold our heads up.

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Gene Helps to Influence Sleep Pattern and Time of Death

According to findings published in the November 2012 issue of Annals of Neurology, a new gene variant has been identified that predicts not only if you’re a morning or night person, but also what time of day you’re likely to die.

Harvard Medical School News reports:

“The internal ‘biological clock’ regulates many aspects of human biology and behavior, such as preferred sleep times, times of peak cognitive performance, and the timing of many physiological processes. It also influences the timing of acute medical events like stroke and heart attack,” says first author Andrew Lim, who conducted the work as a postdoctoral fellow in the Department of Neurology at Beth Israel Deaconess Medical Center.

Lim’s research, which stemmed from an earlier study on sleeping problems and aging led by Dana Alliance member Clifford Saper, M.D., Ph.D., and funded by the Dana Foundation, compared wake-sleep behavior of healthy 65 year olds to their genotypes.

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